The goal is to understand the cellular basis of vision, including the development of the visual system and the role of genetic and environmental factors. The studies will include the analysis of the neural circuitry of the cat and moneky striate cortex using the method of intracellular recording and staining with horse radish peroxidase (HRP). Of special interest is to learn more about the intrinsic horizontal connections and their part in shaping local and global response properties of cortical cells. The functional importance of a given connection will be tested by reversible blocks of a given pathway using local GABA injection. In vitro slices of the striate cortex from cats and monkeys will also be used in studies of circuitry. Specific cell types, retrogradely labelled by injection of fluorescent beads at their site of projection, can be visualized in the living slice for intracellular staining with Lucifer yellow or HRP. The development of specific intracortical connections, such as the clustered horizontal connections, will be studied in kittens of different ages, raised under normal or visually deprived conditions. Color, direction of movement, depth and pattern vision appears to be processed by higher centers through segregated projections to different cortical areas. These projections will be studied in the monkey using single cell staining and reconstruction in combination with histochemical methods. Functional connections between cells in the visual cortex will be studied by correlating the activity of two simultaneously recorded cells. This methods makes it possible to examine the specificity of neural connections with reference to the laminar, columnar and clustered nature of the cortical architecture. The method will be further developed to include an array of up to 32 electrodes for simultaneous recording of many cells, the activity of which will be correlated on line. The correlation between cortical cells can vary with stimulus conditions and the multielectrode array will make it possible to analyze the dynamic neural connections within a small cortical area and perhaps between cortical areas. Another approach to the study of the functional architecture, which has been developed in the laboratory, is an optical recording method. The regional distribution of cortical activity will be examined under different stimulus conditions in both the cat and monkey and related to the response properties of single cells.